Evaporative cooling technique to control the temperature of a vehicle driveline component

ABSTRACT

A system for cooling vehicle driveline components, such as axles or wet disc brake assemblies utilizes evaporative cooling effects of liquid applied to an exterior surface on the housing. A liquid supply is coupled with an outlet and a controller determines when cooling is needed. Liquid is applied onto the housing from the outlet as cooling is needed. One example includes a plurality of fluid collectors on a portion of the housing exterior to increase the amount of liquid maintained on the housing to increase the evaporative cooling effect.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to temperature control forvehicle driveline components. More particularly, this invention relatesto utilizing an evaporative cooling effect to control the temperature ofat least a portion of a driveline component on a vehicle.

[0002] A variety of vehicles are manufactured for a variety of purposes.Examples include passenger vehicles, heavy vehicles such as trucks, andoff road vehicles. Each type of vehicle has particular componentrequirements to meet the needs of the typical situation in which thevehicle is placed during use. Accordingly, a variety of vehiclecomponents have been developed, each having its own benefits and, insome cases, shortcomings or drawbacks.

[0003] In off-road type vehicles, for example, oil in the brake and axleassemblies tends to heat up during braking applications. In many cases,especially in the case of liquid cooled wet disc brakes, the generatedheat exceeds that which can be dissipated by the axle assembly or brakeassembly using normal passive methods.

[0004] The heat build up must be dissipated to maximize component lifeand performance. The fatigue performance of components such as gearsdecreases with incremental rises in temperature. By maintaining anadequate temperature for such components, the fatigue performance isenhanced.

[0005] Vehicle manufacturers and suppliers have been forced to designcomplex and often undesirably costly cooling systems in an attempt toregulate the temperature within the components resulting from brakingapplications. Alternative heat dissipation techniques are needed.

[0006] This invention provides a temperature regulation strategy thateconomically maintains at least a portion of a driveline component, suchas an axle or brake assembly, within a desired operating range.

SUMMARY OF THE INVENTION

[0007] In general terms, this invention is a system for cooling avehicle driveline component that utilizes an evaporative cooling effectfrom applying a liquid to a housing of the component.

[0008] A system designed according to this invention includes a housingthat houses at least portions of the driveline component. A supply ofliquid is supported on the vehicle in some strategic location. An outletis coupled to the supply of liquid and supported relative to the housingsuch that liquid from the outlet is applied onto the housing. The liquidis allowed to evaporate so that it operates to cool the component. Acontroller determines when a temperature of the component is higher thana selected threshold and responsively causes liquid from the supply tobe applied to the housing through the outlet.

[0009] In one example, at least one temperature sensor is associatedwith the driveline component and the temperature sensor communicateswith the controller so that the controller knows when to cause liquid tobe applied to the housing.

[0010] In one example, the housing includes a surface with at least onefluid collector facing generally toward the outlet from which the liquidis applied onto the housing. One example embodiment includes a pluralityof such fluid collectors. The fluid collectors operate to at leasttemporarily maintain more of the liquid on the housing so that a greaterevaporative cooling effect is achieved.

[0011] The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiments. The drawings thataccompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 schematically illustrates a system designed according tothis invention.

[0013]FIG. 2 schematically illustrates an alternative embodiment ofselected portions of the system schematically shown in FIG. 1.

[0014]FIG. 3A schematically illustrates a fluid collector featuredesigned according to one embodiment of this invention.

[0015]FIG. 3B is a cross-sectional illustration taken along the lines3B-3B in FIG. 3A.

[0016]FIG. 4A schematically illustrates an alternative arrangement offluid collectors designed according to an embodiment of this invention.

[0017]FIG. 4B is a cross sectional illustration taken along the lines4B-4B in FIG. 4A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A system 20 for controlling the temperature of a drivelinecomponent 22 is shown schematically in FIG. 1. The illustrated drivelinecomponent 22 includes an axle assembly and a brake assembly, which maybe a wet disc brake assembly, that is particularly useful for off-roadvehicles. In one example, a single housing contains the operative partsof the assemblies. The internal, conventional components of theassemblies are not shown. An axle housing 24 and brake housings 26 and28 are shown. The operation axle assembly and the brake assembliescontrol rotation of wheels 30 to propel the vehicle as known.

[0019] A supply 32 of a cooling liquid 33 preferably is supported on thevehicle in a convenient location. An outlet 34 is associated with thesupply reservoir 32 so that the liquid 33 can be selectively applied tothe component 22 as needed. In the illustrated example, the outlet 34includes conduits 35, 36 and 38 that are positioned to extend over amajority of the surface of the axle housing 24 and the brake housings 26and 28. The liquid 33 selectively is allowed to leave the reservoir 32,flow through the conduits 35, 36 and 38 and to exit openings 40 to driponto the exterior surface of the component housings.

[0020] The size of the supply container 32 may vary depending on thevehicle, the expected need for cooling, the flow rate of the outlets andthe liquid selected, for example. In one example the supply 32 holdsapproximately 20 gallons.

[0021] The example of FIG. 2 shows an alternative where the openings 40are effectively replaced with misting nozzles 42 that apply a sprayedmist of the liquid 33 onto the component housing. In such anarrangement, the liquid preferably is pressurized or otherwise forcedthrough the nozzles 42 to achieve the desired misting effect.

[0022] In one example, the cooling liquid is water. Other solutions arewithin the scope of this invention. Those skilled in the art who havethe benefit of this description will be able to select an appropriateliquid for the needs of their particular situation.

[0023] The example of FIG. 1 includes a plurality of temperature sensors50 associated with the driveline component 22. The illustrated exampleincludes at least one sensor associated with each brake assembly 26 and28. A plurality of sensors 50 are also associated with the axle assembly24. The temperature sensors may be positioned to sense a temperature ofthe respective housings, for example. In another example, thetemperature sensors are positioned within the housing to provide anindication of the temperature of a lubricant within the componentassembly.

[0024] The temperature sensors 50 communicate with a controller 52.Hardware connections may be used or wireless communication between thesensors and the controller. The controller 52 preferably is programmedto recognize the temperature of one or more of the components in thedriveline, which may need cooling, and to determine whether the currenttemperature is above a preselected threshold.

[0025] The controller 52 may be a dedicated microprocessor provided onthe vehicle. A variety of commercially available microprocessors can beused and those skilled in the art who have the benefit of thisdescription will be able to suitably program the controller to achievethe results needed for a particular vehicle under particularcircumstances. Alternatively, the controller 52 may be a dedicatedportion of an engine controller already present on the vehicle. Avariety of such engine controllers are known.

[0026] Whenever the temperature exceeds the threshold, the controller 52preferably controls a supply of the liquid 33 from the reservoir 32 tobe applied onto the component housing. The illustration of FIG. 1includes a control valve arrangement 54 that is operated by thecontroller 52 to regulate the amount of liquid applied to the housing.In another example, such as where the misting nozzles 42 are used, thecontrol valve arrangement 54 includes a pump to pressurize the liquid 33within the system.

[0027] The example illustrated in FIG. 1 relies upon gravity (i.e., thereservoir 32 is positioned higher than the outlet) so that the fluidflow occurs as desired. Given this description, those skilled in the artwill be able to select an appropriate valve or flow control arrangement.One example includes a gravity feed dip tube that relies upon gravity toprovide a constant supply of the liquid ready to be applied to thehousing as needed. A variety of flow control and flow activationstrategies are within the scope of this invention.

[0028] As the liquid 33 is applied onto the housing, at least a portionof it evaporates and provides an evaporative cooling effect to thehousing. This assists in the process of dissipating heat from within thecomponent assembly to reduce the temperature of oil or other lubricantswithin the housing.

[0029] The inventive arrangement provides an economical, robust andeffective way of providing cooling to one or more driveline components.An enhancement to the arrangement shown in FIG. 1 is schematicallyillustrated in FIGS. 3A and 3B. A fluid collector 60 is supported on anexterior surface 62 of the component housing to retain, at leasttemporarily, additional fluid 33 on top of the housing to increase theamount of evaporative cooling. The example schematically illustrated inFIG. 3 includes a rim 64, which may be formed as part of the exteriorhousing or be secured to the housing in a conventional manner. The rim64 and the exterior surface of the housing effectively form a pool orfluid collector 60 where the fluid 33 remains on the surface of thehousing rather than dripping off before evaporation occurs.

[0030] Another arrangement is shown in FIGS. 4A and 4B where a pluralityof fluid collectors 60 are provided on the exterior surface of thehousing 24. In this example, a matrix or mesh of raised surfaces 66 areapplied to the exterior surface of the housing to form the plurality offluid collectors 60. In one example, a prefabricated mesh made fromplastic, metal or a combination of such materials, is secured to theexterior surface of the housing in the region where the cooling liquid33 is applied to the housing. The application method of the mesh willvary depending upon the material selected. The chosen material should beable to retain its shape and, thereby preserve the desired arrangementof the fluid collectors 60, when exposed to expected temperatures thatthe housing will reach.

[0031] In another example, the mesh of surfaces 66 comprises a coatingapplied to the component housing. A conventional masking technique maybe used while a coating is deposited onto the surface to build up thesurfaces 66 surrounding the fluid collectors 60. The depth of the fluidcollectors depends upon the depth of the applied coating or the numberof layers used, for example. Given this description, those skilled inthe art will be able to select from among commercially available paintsor other coating materials to apply a matrix or mesh of the coatingsufficiently thick to achieve a plurality of liquid collectors 60 on atleast a selected portion of the exterior surface of the componenthousing.

[0032] The preceding description is exemplary rather than limiting innature. Variations and modifications to the disclosed examples maybecome apparent to those skilled in the art that do not necessarilydepart from the essence of this invention. The scope of legal protectiongiven to this invention can only be determined by studying the followingclaims.

We claim:
 1. A system for controlling a temperature of a vehicledriveline component, comprising: a housing that houses at least portionsof the driveline component; a supply of liquid supported on the vehicle;an outlet coupled to the supply of liquid that is supported relative tothe housing such that liquid from the outlet is applied onto the housingsuch that the liquid evaporates and operates to cool the component; anda controller that determines when a temperature of the component ishigher than a selected threshold and causes liquid from the supply to beapplied to the housing through the outlet.
 2. The system of claim 1,including a temperature sensor that provides an indication of thetemperature of the component to the controller.
 3. The system of claim2, wherein the temperature sensor is positioned to provide an indicationof the temperature of a lubricant within the housing.
 4. The system ofclaim 1, including a surface on the housing facing generally toward theoutlet, the surface including at least one fluid collector that at leasttemporarily collects some of the fluid applied to the housing.
 5. Thesystem of claim 4, including a plurality of fluid collectors.
 6. Thesystem of claim 5, wherein the housing surface comprises a mesh that issecured to the housing.
 7. The system of claim 6, wherein the meshcomprises at least one of plastic or metal.
 8. The system of claim 4,wherein the surface comprises a coating applied to the housing in apattern that includes at least one region where the coating is notapplied or is thinner than other regions and wherein the at least oneregion forms the collector.
 9. The system of claim 8, wherein thecoating comprises paint.
 10. The system of claim 1, wherein the outletcomprises an opening in a tube through which the liquid drips onto thehousing.
 11. The system of claim 1, wherein the outlet comprises amisting nozzle through which the liquid is sprayed onto the housing. 12.The system of claim 1, wherein the component comprises at least one ofan axle assembly or a wet disc brake assembly or a combination of theaxle assembly and the wet disc brake assembly.
 13. A method of cooling avehicle driveline component that has a housing, comprising the steps of:determining when a temperature of the component is above a chosenthreshold; and applying a liquid to the housing and allowing the liquidto evaporate to thereby cool the component.
 14. The method of claim 13,including dripping water onto the housing.
 15. The method of claim 13,including spraying a mist of water onto the housing.
 16. The method ofclaim 13, including providing a surface on the housing that includes aplurality of liquid collectors that at least temporarily collect theliquid applied the housing to thereby increase an amount of the liquidthat evaporates off from the housing.